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Voltage Control of Multiple Electrochemical Processes during Lithium Ion Migration in NiFe2O4 Ferrite
No full textLi-ion-based electric field control has been attracting significant attention, since it is able to penetrate deep into materials to exhibit diverse and controllable electrochemical processes, which offer more degrees of freedom to design multifunctional devices with low power consumption. As opposed to previous studies that mainly focused on single lithiation/delithiation mechanisms, we reveal three Li-ion modulation mechanisms in the same NiFe2O4 spinel ferrite by in situ magnetometry, i.e., intercalation, conversion, and space charge, which are respectively demonstrated in high, medium, and low voltage range. During the intercalation stage, the spinel structure is preserved, and a reversible modulation of magnetization arises from the charge transfer-induced variation of Fe valence states (Fe2+/Fe3+). Conversion-driven change in magnetization is the largest up to 89 emu g-1, due to the structural and magnetic phase transitions. Although both intercalation and conversion exhibit sluggish kinetics and long response times, the space charge manifests a faster switching speed and superior durability due to its interface electrostatic effect. These results not only provide a clear and comprehensive understanding on Li-based modulation mechanisms but also facilitate multifunctional and multiscenario applications, such as multistate memory, micromagnetic actuation, artificial synapse, and energy storage
Effects of Fe substitution for Mn on structural, magnetic and magnetocaloric properties of TbMn2-xFexSi2
No full textThe structural and magnetic properties of TbMn2-xFexSi2 compounds (x = 0.0–0.4) have been investigated in details by high-resolution synchrotron x-ray and neutron powder diffraction, specific heat, and dc magnetization measurements. The replacement of Fe for Mn in TbMn2-xFexSi2 does not change the crystal structure but leads to a significant contraction of the unit cell (dV/dx ∼ - 6 Å3) and modification of three magnetic phase transition temperatures – the Curie temperatures Tc1, Tc2 and the Néel temperature TN. For example, the Tc1, Tc2 and TN values of TbMn2Si2 decrease from Tc1 = 50 K, Tc2 = 64 K and TN = 500 K to Tc1 = 27 K, Tc2 = 37 K and TN = 440 K for TbMn1.6Fe0.4Si2. Detailed neutron diffraction investigations have allowed us to determine the magnetic structures and construct the magnetic phase diagram as well as confirm the presence of magnetoelastic coupling effects. The significantly different responses of Tc1 and Tc2 to applied magnetic fields (e.g. dTc1/dB = 0.52 K/T and dTc2/dB = 4.7 K/T for TbMn1.6Fe0.4Si2), leads to expansion of the temperature region (ΔT = Tc2 - Tc1) for the canted ferromagnetic state Fmc-ii between Tc1 and Tc2. In the case of TbMn1.6Fe0.4Si2, ΔT increases from ΔT = 9 K for applied magnetic field B = 0.2 T to ΔT = 36 K for B = 6 T, resulting in plateau-like behaviour of magnetic entropy change and enhances the relative cooling power (RCP) in this system. Under a change of magnetic field of 0 T – 5 T, the maximum value of the magnetic entropy changes -ΔSmax and adiabatic temperature change, ΔTad are derived to be -ΔSmax = 13.1 J/kg K and ΔTad = 8.4 K with the RCP = 411 J/kg for x=0.4 sample. The plateau-like magnetocaloric effect and relatively large RCP make these materials potentially suitable for application in cryogenic magnetic refrigeration
Enhancing the mechanical properties of wire arc directed energy deposition Al–Zn–Mg–Cu aluminum alloy through cyclic deep cryogenic treatment
No full textIn this paper, the effects of cyclic deep cryogenic treatment (CDCT) on the mechanical properties and the precipitated phases evolution of 7B55 aluminum alloy produced by wire arc directed energy deposition (WA-DED) were systematically investigated. The findings revealed that, under both T6 and CDCT conditions, the microstructure of the 7B55 aluminum alloy exhibited fine-equiaxed grains. Under the T6 condition, the precipitated phases within the grains were primarily composed of clustered GP zones and η′ phases. Meanwhile, the η phases were continuously distributed along the grain boundaries. Upon subjecting the material to three cycles of CDCT, a noticeable reduction in the number of GP zones within the grains was observed. Simultaneously, there was a substantial increase in the number of η′ phases, accompanied by the occurrence of dislocation lines. The distribution of η phases along the grain boundary transitioned to an interrupted pattern. Under the CDCT-Cycle 3 (CDCT-C3) condition, the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) achieved 658.6 ± 4.5 MPa, 624.2 ± 5.2 MPa, and 8.42 ± 0.18 %, respectively. However, with the progression to four cycles of CDCT, the GP zones within the grains disappeared and the number of η′ phases started to decrease with the formation of a large number of η phases. The η phase along the grain boundary continuously grew by merging and absorbing solute atoms from the Al matrix near the grain boundaries. This led to the formation of coarsen and interrupted η phases and the Precipitate-Free Zone (PFZ) along the grain boundaries. Subsequently, the mechanical properties experienced a substantial decrease after the CDCT-Cycle 4 (CDCT-C4)
Effects of a staff physical activity professional development intervention on preschoolers' mental health and self-regulation: The active learning Norwegian Preschool(er)s (ACTNOW) cluster randomised controlled trial
No full textBackground and aim: Physical activity may have positive effects on preschoolers' mental health and self-regulation. The preschool setting provides children with opportunities to meet physical activity guidelines and could improve with staff training in delivering physical activity. This study examined the effect of physical activity professional development for preschool staff on preschoolers' proxy-measured mental health and self-regulation. Methods: In total, 1265 children from 46 preschools were cluster randomised to either the intervention or the control group. The intervention was nested within two levels implemented concurrently: the preschool level, formed as a professional development where preschools conducted development work, and the child level, with whom the staff implemented physical activity with four core components. Data were analysed using an ANCOVA model through structural equation modelling with latent outcome factors of: emotional problems, peer problems, hyperactivity, and prosocial behaviour from the Strength and Difficulties Questionnaire; and cognitive, emotional, and behavioural self-regulation from the Child Self-regulation and Behaviour Questionnaire. Results: No effects of the intervention (standardised effect sizes -0.195–0.145, p-values 0.118–0.893) were observed. Secondary analysis showed that children with initially high prosocial behaviour and behavioural self-regulation positively benefited from the intervention (p = 0.035 and p = 0.047, respectively). Conclusion: The ACTNOW intervention had no effects on preschoolers' mental health or self-regulation after 18 months, besides effects for children with initially the highest prosocial behaviour and behavioural self-regulation. Although the professional development was more extensive than previous studies it may have been insufficient to change the preschools physical activity practices. Clinical trial registration: www.ClinicalTrials.gov identifier NCT04048967
Potassium Phthalimide Doped with Delta-Site Structures to Construct Ultra-Long Cycle Life Aqueous Zn-Polymer Batteries
No full textAqueous Zn-polymer batteries hold great promise for environmentally friendly energy storage systems. However, the poor cycling performance caused by irreversible structural deformation and polymer chain entanglement during the embedding and de-embedding processes of Zn2+ and H+ ions is one of the key challenges facing their development. Here a new polyaniline cathode doped is developed with potassium phthalimide using a secondary doping approach. This polymeric electrode integrates the conjugated backbone for charge transport with an anionic phthalimide dopant for constructing a triangular-site structure, as illustrated by the density functional theory calculations. This unique molecular structure is favorable for improving conductivity and structural stability by effectively modulating the localized electron cloud density. The Zn-polymer battery holds an outstanding capacity retention of 76.1% after 25,000 cycles at a current density of 1 A g−1 with the coulombic efficiency maintained above 99.4%. This secondary doped polymer strategy offers a new host alternative for the ultra-long cycle life of Zn-polymer batteries. The molecular design strategy and the insight into the relationship between the structure and performance may provide some guidelines for developing polymer cathodes with high stability
A multi-period restoration approach for resilience increase of active distribution networks by considering fault rapid recovery and component repair
No full textAs the frequency of extreme weather events continues to rise, there is an urgent need to strengthen the safe and stable operation of active distribution networks (ADNs), and it is of great value to establish highly resilient ADNs to withstand multi-faults caused by extreme weather events. This paper proposes a multi-period restoration approach for the resilience increase of ADNs by considering fault rapid recovery and component repair under typhoon disasters. Firstly, based on the structural reliability theory, the failure rate model of the main components is established, and in light of the system information entropy, the typical fault scenario selection strategy is designed to determine the branches with high fault probability. Then, according to the fault islanding division and network reconfiguration, a fault rapid recovery method is suggested for the ADNs, where the impact of typhoon disasters on the output features of distributed generators (DGs) are taken into account, and meanwhile, the network structure and the output power of the DGs are jointly optimized to minimize the operating cost of the ADNs. Further, a fault component repair model is formulated by adopting the adaptive ant colony algorithm, and a multi-period restoration approach is proposed for the ADNs to fulfill a rolling optimization of the network reconfiguration and fault component repair. The improved IEEE 33-node and IEEE 118-node systems are used for the approach verification, and the results show that the proposed approach can effectively improve the overall load restoration level and increase the component repair efficiency. Following a multi-criteria resilience evaluation system, the proposed approach enables the ADNs to more effectively withstand typhoon disasters, offering a resilience increase of 6.93 % and 32.24 % regarding the 33-node and 118-node systems
Phytoremediating the air down under: Evaluating airborne particulate matter accumulation by 12 plant species in Australia
No full textAtmospheric particulate matter (PM) is the most inhaled hazardous air pollutant that can cause adverse health impacts. Plants can remove such contaminants and act as biological filters through phytoremediation. In this study, we screened 12 Australian native species (two deciduous trees, three evergreen shrubs, and seven evergreen trees) growing in three regions to determine their potential in accumulating leaf surface (SPM) and in-wax PM (WPM). Among the screened species, Lagunaria patersonia (139.22 μg cm−2) was the most effective PM accumulator, followed by Ficus obliqua (131.02 μg cm−2). L. patersonia is an Australian native tree with a dense crown that can efficiently trap PM due to air turbulence between its leaves and branches; broad leaves with a rough texture enhance the plant's ability to trap PM. On the contrary, morphological characteristics like evergreen leaves with hairy appendages may act as an efficient trap for PM in F. obliqua. Due to smoother leaves, the least effective species were F. rubignosa and Eucalyptus saligna. In addition to leaf shape, leaf structures and micromorphology influence PM accumulation. For instance, Pittosporum undulatum accumulated more PM due to its wrinkled and folded leaf structures despite a significantly lower waxes layer. The findings highlight the importance of planting efficient PM accumulator species to shield vulnerable areas from pollution and decrease human exposure to pollutants. The sink capacity of these species can be used in urban tree planning to combat air pollution and improve air quality.</p
Widely valued but differently experienced; understanding relationships with greenspace in the CBD
No full textValuing nature through attention to urban greening offers some remedy to ‘Extinction of Experience’ – the decline in diversity and quality of people's relationships to nature. Unfortunately, while the role and value of greenspaces are increasingly recognised, recognition and valuing does not always translate into beneficial experiences for urban dwellers. This study examined people's relationships to greenspaces in the central business district (CBD) of Liverpool, New South Wales, Australia. Liverpool is a rapidly growing hub in outer metropolitan Sydney, where provision of greenspaces is generally acknowledged as inadequate. Space for plants is limited in city CBDs and these environments are especially challenging places to green, meaning that the quality of vegetation available for users is also often limited. Here, we report on an online survey conducted over the summer of 2019–2020, coinciding with the catastrophic Australian ‘black summer’ bushfires. It explored how people valued, used and experienced existing greenspaces in the CBD. Quantitative and qualitative results from 196 respondents illustrate that although most people agree on the benefits of greenspace, value it positively and use it regularly, three persistent concerns mediate their experiences: lack of shade, poor maintenance, and poor facilities. Further, and in addition to within space variation, experiences of greenspaces are negatively influenced by distance travelled and other barriers to what might otherwise be quality spaces. As the urban environment of Liverpool's CBD undergoes rapid transformation to a higher activity (business/retail/services) and denser residential environment, there is an opportunity to translate the differences between values and experiences illustrated here to improve the design and quality of future greenspace. More broadly, this study indicates why the spatial dimensions of people's relationships to urban nature requires more explicit and critical consideration within experience research
Revealing the interfacial chemistry of silicon anodes with polysiloxane electrolyte additives
No full textSilicon (Si) anodes are promising in lithium-ion batteries owing to their high specific capacity and suitable voltage platform. However, particle volume expansion (>300 %) and the continuous consumption of Li+ to form new interfacial layers result in poor cycle performance. We report a sustainable low-cost Si material derived from photovoltaic cutting waste, showing a high initial Coulombic efficiency (86.9 %). The cycle stability of Si/graphite is enhanced in terms of a 38 % capacity retention increase in the presence of vinyl-terminated polydimethylsiloxane (Vi-PDMS) additive. The C = C bond in Vi-PDMS plays a role in reacting with hydrogen fluoride (HF) by-products to prevent the side reaction between HF and solvent. The decomposed macromolecule Si-containing Li salt serves as a part of the solid electrolyte interphase film and has low interface resistance. This formed interphase layer effectively mitigates stress concentration at the contact surface between silicon particles and the current collector caused by expansion forces
Observed relationships between nap practices, executive function, and developmental outcomes in Tunisian childcare centers
No full textThe objective of this design was to conduct an observational study comparing anthropometric characteristics, cognitive functions, as well as gross and fine motor skills. The study included 118 preschool-aged children (47 boys, 71 girls) enrolled in childcare centers. They were categorized into two groups based on their nap habits. The nap group comprised 59 children (23 boys, 36 girls), age (mean ± standard deviation) ([3.96 ± 0.54] years) who took naps after lunch, while the no-nap group included 59 children (24 boys, 35 girls) age (mean ± standard deviation) ([4.18 ± 0.61] years) who remained awake during this period. The results showed that the napping group had significantly higher scores for body mass index (BMI) (p < 0.000 1), height-for-age z score (HAZ) (p = 0.003), and higher BAZ (BMI-for-age z score) scores (p < 0.000 1), compared to the No-nap group. In terms of cognitive function, the study revealed that the napping group had better working memory performance compared to the No-nap group (p = 0.002), but no significant impact on inhibition was observed. The results also showed that taking a nap may improve functional mobility (p = 0.003) and upper body strength (p = 0.026) especially in boys. Future research could investigate the long-term effects of inadequate nap time on children's health and development and also develop and evaluate interventions to improve nap time habits in preschool children